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Date: Thu, 19 Mar 2015 11:16:13 -0500 (CDT)
From: Christoph Lameter <cl@linux.com>
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To: Joonsoo Kim <js1304@gmail.com>
cc: Mark Rutland <mark.rutland@arm.com>, LKML <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Catalin Marinas <Catalin.Marinas@arm.com>,
        David Rientjes <rientjes@google.com>,
        Jesper Dangaard Brouer <brouer@redhat.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Pekka Enberg <penberg@kernel.org>,
        Steve Capper <steve.capper@linaro.org>
Subject: Re: [PATCHv2] mm/slub: fix lockups on PREEMPT && !SMP kernels
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On Thu, 19 Mar 2015, Joonsoo Kim wrote:

> > I was under the impression that this_cpu operations would always result
> > in an access, much like the *_ONCE accessors, so we should aways redo
> > the access for this_cpu_read(s->cpu_slab->tid). Is that not the case?
>
> I'm not the expert on that operation. Christoph could answer it.

this_cpu_read() always generates a load via an asm instruction.